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Gas Sensing Nanomaterials and Sensors

Works Count: 102100

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This cluster of papers focuses on the development, materials, and mechanisms of gas sensing technology, with an emphasis on metal oxide-based gas sensors, nanomaterials, semiconductors, and room temperature operation. It also covers the application of gas sensors for selective detection of various gases and humidity sensing.

Keywords

Gas Sensors; Metal Oxide; Nanomaterials; Semiconductors; Gas Sensing Mechanisms; Room Temperature; Nanostructures; Humidity Sensors; Chemical Sensors; Selective Detection

Chemical Sensing with Solid State Devices

1989-01-01

Marc Madou , Steven R. Morrison

SnO2: A comprehensive review on structures and gas sensors

2014-07-05

Soumen Das , V. Jayaraman

Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review

2004-07-01

G. Eranna , B. C. Joshi , D. P. Runthala +1 more

ABSTRACT In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though … ABSTRACT In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer a wide spectrum of materials and their sensitivities for different gaseous species, making it a better choice over other options. In this article a critical parameter analysis of different metal oxides that are known to be sensitive to various gaseous species are thoroughly examined. This includes phase of the oxide, sensing gaseous species, operating temperature range, and physical form of the material for the development of integrated gas sensors. The oxides that are covered in this study include oxides of aluminum, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, indium, iron, manganese, molybdenum, nickel, niobium, ruthenium, tantalum, tin, titanium, tungsten, vanadium, zinc, zirconium, and the mixed or multi-component metal oxides. They cover gases such as CO, CO2, CH4, C2H5OH, C3H8, H2, H2S, NH3, NO, NO2, O2, O3, SO2, acetone, dimethylamine (DMA), humidity, liquid petroleum gas (LPG), petrol, trimethylamine (TMA), smoke, and many others. Both doped and undoped oxides are analyzed for the compatibility with silicon processing conditions and hybrid microcircuit fabrication techniques. In silicon processing conditions, they are further analyzed for the suitability for simple silicon surfaces, silicon-on-insulator (SOI) surfaces, and micromachined silicon geometries for different operating temperatures. Discussion on gas-sensing properties of each material and its applications are described in the text in alphabetical order of the elemental oxides. Further, the gas-sensing properties like sensitivity, detection limits, operating temperature, and so on are summarized in tables al ong with relevant references. The figures incorporated in the present review are primarily based on discussions and data in tables. However, these figures provide a qualitative comparison and present a pictorial view to examine suitability of a material for a particular application. From the known parameters, the present study clearly indicates the suitability of certain materials and the gases that they cover for the development of integrated micro gas sensors. A clear picture has been brought out for the development of silicon-based processing technology. Various parameters are discussed for the selection of these materials, to examine their suitability and practical problems that are being associated. Etching of these metal oxides and the reliability of devices are also discussed.

Fabrication of Single‐ and Multilayer MoS2 Film‐Based Field‐Effect Transistors for Sensing NO at Room Temperature

2011-10-20

Hai Li , Zongyou Yin , Qiyuan He +7 more

Single- and multilayer MoS2 films are deposited onto Si/SiO2 using the mechanical exfoliation technique. The films were then used for the fabrication of field-effect transistors (FETs). These FET devices can … Single- and multilayer MoS2 films are deposited onto Si/SiO2 using the mechanical exfoliation technique. The films were then used for the fabrication of field-effect transistors (FETs). These FET devices can be used as gas sensors to detect nitrous oxide (NO). Although the single-layer MoS2 device shows a rapid response after exposure to NO, the current was found to be unstable. The two-, three-, and four-layer MoS2 devices show both stable and sensitive responses to NO down to a concentration of 0.8 ppm. Two-dimensional nanomaterials have received much attention in recent years owing to their unusual properties that stem from their quantum and surface effects.1-26 Graphene,27, 28 a single-layer 2D carbon material, exhibits exceptional physical properties such as a high electron conductivity and excellent mechanical strength. Very recently, other 2D semiconducting nanomaterials like transition metal dichalcogenides have also attracted significant research interest and hold great potential for many applications.9, 11, 13, 14, 16, 18, 24, 25 For example, MoS2, one kind of the transition metal dichalcogenide, is currently being explored and used in lubrication, as a catalyst for hydrodesulfonization, and for photoelectrochemcial hydrogen production.29-32 Single-layer MoS2 prepared from mechanical exfoliation exhibits a dramatically increased luminescence quantum efficiency compared to its bulk counterpart.16 Mechanically exfoliated MoS2 monolayers have also been used to fabricate field-effect transistors (FETs) with high mobilities and current On/Off ratios exceeding 1 × 108 at room temperature, which is comparable to those obtained in graphene nanoribbon-based FETs.9 Hence, it is of scientific importance to synthesize and characterize MoS2 sheets ranging from a single layer to a few layers in order to better apply them in various applications. Detection of environmental pollution, especially toxic gas, is important and critical to industry, agriculture, and public health.33 For example, NOx gas is one of the most common air pollutants. It is a source of acid rain and can cause serious diseases.8 As such, there is an increasing demand to develop highly sensitive, low cost, and portable gas sensors with low power consumption.2 Electronic gas sensors based on FETs have shown promising results.2, 4-6, 8, 26, 33-35 One-dimensional semiconductors, such as carbon nanotubes33-35 and semiconductor nanowires,36-38 are popular channel materials used for FET-based sensors. 2D graphene sheets are also favored in electronic sensing because of their unique electronic properties and large specific surface area.1-8 In addition, the 2D configuration of graphene sheets, compared to 1D semiconductors, allows for the better adsorption of gas molecules and leads to lower electrical noise and lower detection limits.2, 4-6, 26 As a result, the graphene-based gas sensor has achieved a sensitivity down to the single-molecule level.2 MoS2 sheets, the semiconducting analogue of graphene, are thus expected to be a potential candidate for sensing applications. In this communication, we report a systematic study of the fabrication of single- and multilayer MoS2 films using the mechanical exfoliation method. The fabricated MoS2 FET devices show n-type doping behavior. As a proof of concept, the single- and multilayer MoS2 FETs were used to detect the adsorption of NO. It was found that the FET sensors based on bilayer (2L), trilayer (3L), and quadrilayer (4L) MoS2 films exhibited a high sensitivity to NO with detection limit of 0.8 ppm, while the single-layer (1L) MoS2 device showed a rapid but unstable response. Single- and multilayer MoS2 nanosheets were deposited onto Si substrates covered with a 300 nm-thick SiO2 layer, referred to as Si/SiO2, using the mechanical exfoliation technique.1, 9, 15 Similar to graphene, MoS2 nanosheets with different layer numbers show distinguishable contrast on the Si/SiO2 substrates, as observed by optical microscopy (Figure 1A–D). The thicknesses of MoS2 films with different optical contrasts (Figure 1A–D) were measured by AFM (Figure 1E–H), which showed that the average height of a single layer of MoS2 (Figure 1A) is ≈0.8 nm (Figure 1E), which is consistent with previous reports.9, 15, 18 The heights of 2L, 3L, and 4L MoS2 sheets (Figure 1B–D) measured by AFM are 1.5, 2.1, and 2.9 nm, respectively (Figure 1F–H). Mechanically exfoliated single- and multilayer MoS2 films on Si/SiO2. Optical microscope images of single-layer (1L), bilayer (2L), trilayer (3L), and quadrilayer (4L) MoS2 films (A–D). Panels E–H show the corresponding AFM images of the 1L (thickness: ≈0.8 nm), 2L (thickness: ≈1.5 nm), 3L (thickness: ≈2.1 nm), and 4L (thickness: ≈2.9 nm) MoS2 films shown in (A–D). Figure 2 shows the Raman spectra of single- and multilayer MoS2 films. Single-layer MoS2 exhibited strong bands at 384 and 400 cm−1, which are associated with the in-plane vibrational (E1 2g) and the out-of-plane vibrational (A1g) modes, respectively.10, 15 As the layer number increased from 1L to 4L, a red-shift of the E1 2g band and a blue-shift of the A1g bands were observed (see Figure 2), which is in consistent with the previous report.15 Raman spectra of single- and multilayer (1L to 4L) MoS2 films. FET devices are fabricated with exfoliated 1L to 4L MoS2 films. As an example, a 2L MoS2 film and its corresponding FET device are shown in Figures 3A and 3B, respectively. The recorded Ids–Vg curve (Figure 3C) is typical of the 2L MoS2 FET with an n-type channel, which is in agreement with the previous report.9 In fact, all the MoS2 FET devices investigated here possess n-type doping character (see Figure S1, Supporting Information (SI)). The current On/Off ratio of 2L, 3L, and 4L MoS2 devices is above 103 (Vg from -10 to 10 V), while it is comparably smaller (≈102) for the 1L MoS2 FET. It is important to note that our devices show a lower On/Off ratio compared to the previously reported single-layer MoS2 transistor, in which a mobility booster (HfO2) was used.9 A) Optical microscope image of a bilayer (2L) MoS2 film deposited onto Si/SiO2. B) Optical microscope image of an FET device based on the 2L MoS2 film shown in (A), where Au electrodes work as the source and drain electrodes and the substrate acts as the back gate. C) Plot of Ids vs. Vg of the 2L MoS2 FET shown in (B) at Vds = 3 V. Inset: Ids–Vds curves at different Vg ranging from −10 to 10 V. As a proof of concept, the as-fabricated single- and multilayer MoS2 FETs were used to detect NO gas at room temperature. In these experiments, Ti/Au was deposited as drain and source electrodes and the MoS2 sheets were the active channels. We found that the current response of a single-layer MoS2 device is not stable (see Figure S2, SI). Contrary to this, the devices fabricated with 2–4L MoS2 films showed much better performance. Figure 4A shows a typical current response of a 2L MoS2 FET device upon exposure to NO with concentrations ranging from 0.3 to 2 ppm. The decrease in current, i.e., increase in resistance, upon exposure of the device to NO is most likely due to the p-doping effect,2, 4, 6, 39 which is consistent with the charge transfer mechanism taking place in the 2D graphene3 and 1D carbon nanotube34 based gas sensors. NO sensor based on 2L MoS2 FET device. A) Real-time current response after exposure of the 2L MoS2 FET to NO with increased concentration. Inset: A typical adsorption and desorption process of NO on the 2L MoS2 FET. B) Plot of the percent change in current as a function of NO concentration. The complete desorption of adsorbed NO molecules upon N2 flow is very slow, which is possibly due to the strong chemisorption of NO on the MoS2 surface. Interestingly, both the adsorption and desorption processes of NO can be divided into two steps (a rapid one and a slow one). In a typical adsorption process (see Figure 4A inset), the current dropped immediately after the device was exposed to NO. This lasted about 30 s (the rapid step, left solid line) and then continuously decreased for more than 2 min until the saturation of NO adsorption was reached (the slow step, left dashed line). The same two-step process was observed for NO desorption (right solid and dashed lines in the inset in Figure 4A). A similar phenomenon was also observed in the graphene-based gas sensors, in which it was attributed to the different binding energies of gas molecules at the different defect sites on the graphene surface.4 However, the detailed interaction between the MoS2 surface and the gas molecules is not clear here, which requires further investigation. The responses from 3L and 4L MoS2 devices (see Figure S3, SI) are similar to those of the 2L MoS2 device. Figure 4B shows a plot of percent change in current in the 2L MoS2 FET as a function of NO concentration (calculated from Figure 4A). Although the current response is very high (80% decreased at 2 ppm), the detection limit is compromised by the low signal-to-noise ratio (at 0.8 ppm the signal-to-noise ratio is approximately 3). Such a low signal-to-noise ratio might arise from our homemade gas-sensing system, since the sensing chamber is relatively big (>1000 L). On the contrary, the single-layer MoS2 based device exhibited a much faster (decrease of 50% in current within 5 s in 0.3 ppm NO) but a rather unstable current response (see Figure S2, SI). The reason for this is not clear and further study is required. In summary, single- and multilayer (1–4L) MoS2 films were deposited onto Si/SiO2 substrates using the scotch tape-based mechanical exfoliation technique. The layer numbers of MoS2 films are confirmed by Raman spectroscopy and AFM. FETs based on single- and multilayer MoS2 sheets, exhibiting the n-type semiconducting properties, have been successfully used for sensing NO gas. Although the single-layer MoS2 FET showed a rapid and dramatic response upon exposure to NO, its current was found to be unstable. Contrary to this, the 2L, 3L, and 4L MoS2 FET devices exhibit both stable and sensitive responses down to a detection limit of 0.8 ppm NO. Our experimental results presented here expand the potential application of 2D MoS2 FETs in gas sensing. Mechanical Exfoliation of MoS2: Single- and multilayer MoS2 films were isolated from bulk MoS2 (429MM-AB,SPI molybdenum disulfide, single crystals from Canada, SPI Supplies Inc., USA) and then deposited onto the freshly cleaned Si substrates covered by a 300 nm thick SiO2 layer using the scotch tape-based mechanical exfoliation method, which is widely employed for preparation of single-layer graphene sheets.1 Optical microscope (Eclipse LV100D, Nikon) was used to locate the single- and multilayer MoS2 films. As shown in Figure 1A–D, single and multilayer MoS2 films showed clear optical contrast against the substrate. Bright flakes were observed when the layer number of MoS2 exceeded 10 (Figure 1A and 1D). AFM (Dimension 3100 with Nanoscope IIIa controller, Veeco, CA, USA) was used to confirm the layer number by measuring the film thicknesses in tapping mode in air. Raman Spectroscopy: Analysis of the single- and multilayer MoS2 films by Raman spectroscopy was carried out on a WITec CRM200 confocal Raman microscopy system with the excitation line of 488 nm and an air-cooling charge-coupled device (CCD) as the detector (WITec Instruments Corp, Germany). The Raman band of Si at 520 cm−1 was used as a reference to calibrate the spectrometer. Fabrication, Characterization and Sensing Applications of MoS2 FETs: The source and drain electrodes of MoS2 FET devices were fabricated by traditional photolithography. The channel length for all FET devices was kept at ≈3 μm. The 5 nm Ti/50 nm Au, used as source and drain electrodes, was deposited by the electron beam evaporator. After removal of the photoresist, the electrical properties of the fabricated MoS2 FETs were tested by the Keithley 4200 semiconductor characterization system in air at room temperature. The as-prepared MoS2 FET devices were located in the chamber of the homemade sensing equipment. Keithley 4200 semiconductor characterization system was used to monitor the current change in real-time using the two-point measurement in a glove box. NO (2 ppm in N2) and N2 (99.999%) cylinders (National Oxygen Pte Ltd, Singapore) with attached flow meters were used to adjust the concentration of the NO gas. Supporting Information is available from the Wiley Online Library or from the author. This work was supported by AcRF Tier 2 (ARC 10/10, No. MOE2010-T2-1-060) from MOE, CREATE program (Nanomaterials for Energy and Water Management) from NRF, and New Initiative Fund FY 2010 (M58120031) from NTU in Singapore. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors

2004-04-26

Qing Wan , Q. H. Li , Yujin Chen +4 more

Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited … Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited high sensitivity and fast response to ethanol gas at a work temperature of 300 °C. Our results demonstrate the potential application of ZnO nanowires for fabricating highly sensitive gas sensors.

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New approaches for improving semiconductor gas sensors

1991-08-01

Noboru Yamazoe

SnO2 sensors: current status and future prospects

1995-01-01

Wolfgang Göpel , Klaus Schierbaum

Enhanced Gas Sensing by Individual SnO2 Nanowires and Nanobelts Functionalized with Pd Catalyst Particles

2005-03-04

Andrei Kolmakov , D. O. Klenov , Yigal Lilach +2 more

The sensing ability of individual SnO2 nanowires and nanobelts configured as gas sensors was measured before and after functionalization with Pd catalyst particles. In situ deposition of Pd in the … The sensing ability of individual SnO2 nanowires and nanobelts configured as gas sensors was measured before and after functionalization with Pd catalyst particles. In situ deposition of Pd in the same reaction chamber in which the sensing measurements were carried out ensured that the observed modification in behavior was due to the Pd functionalization rather than the variation in properties from one nanowire to another. Changes in the conductance in the early stages of metal deposition (i.e., before metal percolation) indicated that the Pd nanoparticles on the nanowire surface created Schottky barrier-type junctions resulting in the formation of electron depletion regions within the nanowire, constricting the effective conduction channel and reducing the conductance. Pd-functionalized nanostructures exhibited a dramatic improvement in sensitivity toward oxygen and hydrogen due to the enhanced catalytic dissociation of the molecular adsorbate on the Pd nanoparticle surfaces and the subsequent diffusion of the resultant atomic species to the oxide surface.

Semiconducting metal oxides as sensors for environmentally hazardous gases

2011-08-23

Khatcharin Wetchakun , T. Samerjai , Nittaya Tamaekong +6 more

Humidity Sensors Principle, Mechanism, and Fabrication Technologies: A Comprehensive Review

2014-04-30

Hamid Farahani , Rahman Wagiran , Mohd Nizar Hamidon

Humidity measurement is one of the most significant issues in various areas of applications such as instrumentation, automated systems, agriculture, climatology and GIS. Numerous sorts of humidity sensors fabricated and … Humidity measurement is one of the most significant issues in various areas of applications such as instrumentation, automated systems, agriculture, climatology and GIS. Numerous sorts of humidity sensors fabricated and developed for industrial and laboratory applications are reviewed and presented in this article. The survey frequently concentrates on the RH sensors based upon their organic and inorganic functional materials, e.g., porous ceramics (semiconductors), polymers, ceramic/polymer and electrolytes, as well as conduction mechanism and fabrication technologies. A significant aim of this review is to provide a distinct categorization pursuant to state of the art humidity sensor types, principles of work, sensing substances, transduction mechanisms, and production technologies. Furthermore, performance characteristics of the different humidity sensors such as electrical and statistical data will be detailed and gives an added value to the report. By comparison of overall prospects of the sensors it was revealed that there are still drawbacks as to efficiency of sensing elements and conduction values. The flexibility offered by thick film and thin film processes either in the preparation of materials or in the choice of shape and size of the sensor structure provides advantages over other technologies. These ceramic sensors show faster response than other types.

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Mechanisms behind green photoluminescence in ZnO phosphor powders

1996-05-15

K. Vanheusden , W. L. Warren , C. H. Seager +3 more

We explore the interrelationships between the green 510 nm emission, the free-carrier concentration, and the paramagnetic oxygen-vacancy density in commercial ZnO phosphors by combining photoluminescence, optical-absorption, and electron-paramagnetic-resonance spectroscopies. We … We explore the interrelationships between the green 510 nm emission, the free-carrier concentration, and the paramagnetic oxygen-vacancy density in commercial ZnO phosphors by combining photoluminescence, optical-absorption, and electron-paramagnetic-resonance spectroscopies. We find that the green emission intensity is strongly influenced by free-carrier depletion at the particle surface, particularly for small particles and/or low doping. Our data suggest that the singly ionized oxygen vacancy is responsible for the green emission in ZnO; this emission results from the recombination of a photogenerated hole with the singly ionized charge state of this defect.

Nanoscale metal oxide-based heterojunctions for gas sensing: A review

2014-07-29

D. R. Miller , Sheikh A. Akbar , Patricia A. Morris

A New Detector for Gaseous Components Using Semiconductive Thin Films.

1962-10-01

Tetsuro Seiyama , Akio Kato , Kiyoshi Fujiishi +1 more

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Detector for Gaseous Components Using Semiconductive Thin Films.Tetsuro Seiyama, Akio Kato, Kiyoshi Fujiishi, and Masanori NagataniCite this: Anal. Chem. 1962, 34, 11, 1502–1503Publication Date (Print):October … ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Detector for Gaseous Components Using Semiconductive Thin Films.Tetsuro Seiyama, Akio Kato, Kiyoshi Fujiishi, and Masanori NagataniCite this: Anal. Chem. 1962, 34, 11, 1502–1503Publication Date (Print):October 1, 1962Publication History Published online1 May 2002Published inissue 1 October 1962https://pubs.acs.org/doi/10.1021/ac60191a001https://doi.org/10.1021/ac60191a001research-articleACS PublicationsRequest reuse permissionsArticle Views4530Altmetric-Citations1180LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Toward innovations of gas sensor technology

2005-02-17

Noboru Yamazoe

Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

2010-03-15

Cheng‐Xiang Wang , Longwei Yin , Luyuan Zhang +2 more

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface … Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above.

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Selected-Control Hydrothermal Synthesis of α- and β-MnO2 Single Crystal Nanowires

2002-03-01

Xun Wang , Yadong Li

A selective-control hydrothermal method has been developed in the preparation of α- and β-MnO2 single-crystal nanowires. The crystal structure and morphology of the final products can be influenced by the … A selective-control hydrothermal method has been developed in the preparation of α- and β-MnO2 single-crystal nanowires. The crystal structure and morphology of the final products can be influenced by the concentration of NH4+ and SO42-.

Hydrogen sensors – A review

2011-04-30

Thomas Hübert , L. Boon-Brett , George Black +1 more

Field-Effect Transistors Based on Single Semiconducting Oxide Nanobelts

2002-12-28

Michael S. Arnold , Phaedon Avouris , Zhengwei Pan +1 more

We have fabricated field-effect transistors (FETs) based on single SnO2 and ZnO nanobelts of thicknesses between 10 and 30 nm. Switching ratios as large as 6 orders of magnitude and … We have fabricated field-effect transistors (FETs) based on single SnO2 and ZnO nanobelts of thicknesses between 10 and 30 nm. Switching ratios as large as 6 orders of magnitude and conductivities as high as 15 (Ω cm)-1 are observed. Annealing SnO2 nanobelt FETs in an oxygen-deficient atmosphere produces a negative shift in gate threshold voltage, indicating doping by the generation of surface oxygen vacancies. This treatment provides an effective way of tuning the electrical performance of the nanobelt devices. The ability of SnO2 FETs to act as gas sensors is also demonstrated. SnO2 FETs with lengths of about 500 nm or less show an anomalous behavior where the conductance cannot be modulated by the gate. ZnO nanobelt FETs are sensitive to ultraviolet light. Both photogeneration of electron−hole pairs and doping by UV induced surface desorption contribute to the conductivity.

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

2010-06-01

George F. Fine , L.M. Cavanagh , Ayo Afonja +1 more

Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit … Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition.

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Grain size effects on gas sensitivity of porous SnO2-based elements

1991-02-01

Chao‐Nan Xu , Jun Tamaki , Norio Miura +1 more

The surface and materials science of tin oxide

2005-01-01

Matthias Batzill , Ulrike Diebold

Detection of CO and O2 Using Tin Oxide Nanowire Sensors

2003-06-16

Andrei Kolmakov , Yuxuan Zhang , Guosheng Cheng +1 more

Highly uniform SnO 2 nanowires , with bulk electronic properties directed by their surface chemistry, have been produced by isolating and oxidizing tin nanowires selected from a template‐synthesized array. The … Highly uniform SnO 2 nanowires , with bulk electronic properties directed by their surface chemistry, have been produced by isolating and oxidizing tin nanowires selected from a template‐synthesized array. The nanowires act as sensitive, fast, stable, and reproducible gas sensors that can be easily integrated into a multi‐component array (see Figure).

Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts

2002-08-30

Elisabetta Comini , G. Faglia , Giorgio Sberveglieri +2 more

Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and … Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts. Electrical characterization showed that the contacts were ohmic and the nanobelts were sensitive to environmental polluting species like CO and NO2, as well as to ethanol for breath analyzers and food control applications. The sensor response, defined as the relative variation in conductance due to the introduction of the gas, is 4160% for 250 ppm of ethanol and −1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate the potential of fabricating nanosized sensors using the integrity of a single nanobelt with a sensitivity at the level of a few ppb.

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Nearly Monodisperse Cu2O and CuO Nanospheres: Preparation and Applications for Sensitive Gas Sensors

2006-01-28

Jiatao Zhang , Junfeng Liu , Qing Peng +2 more

Nearly monodisperse single-crystalline Cu2O nanospheres were prepared by an effective solution method with NaBH4 as the reducing agent. Sensors based on them have good sensitivity to some flammable gases because … Nearly monodisperse single-crystalline Cu2O nanospheres were prepared by an effective solution method with NaBH4 as the reducing agent. Sensors based on them have good sensitivity to some flammable gases because thin films formed by nanospheres have capacious interspaces and enough spherical surfaces to interact with gases (ppm level).

Photoelectrolysis and physical properties of the semiconducting electrode WO2

1977-05-01

M. A. Butler

The behavior of semiconducting electrodes for photoelectrolysis of water is examined in terms of the physical properties of the semiconductor. The semiconductor-electrolyte junction is treated as a simple Schottky barrier, … The behavior of semiconducting electrodes for photoelectrolysis of water is examined in terms of the physical properties of the semiconductor. The semiconductor-electrolyte junction is treated as a simple Schottky barrier, and the photocurrent is described using this model. The approach is appropriate since large-band-gap semiconductors have an intrinsic oxygen overpotential which removes the electrode reaction kinetics as the rate-limiting step. The model is successful in describing the wavelength and potential dependence of the photocurrent in WO3 and allows a determination of the band gap, optical absorption depth, minority-carrier diffusion length, flat-band potential, and the nature of the fundamental optical transition (direct or indirect). It is shown for WO3 that minority-carrier diffusion plays a limited role in determining the photoresponse of the semiconductor-electrolyte junction. There are indications that the diffusion length in this low carrier mobility material is determined by diffusion-controlled bulk recombination processes rather than the more common trap-limited recombination. It is also shown that the fundamental optical transition is indirect and that the band-gap energy depends relatively strongly on applied potential and electrolyte. This effect seems to be the result of field-induced crystallographic distortions in antiferroelectric WO3.

Metal oxide-based gas sensor research: How to?

2006-10-28

Nicolae Bârsan , Dorota Koziej , Udo Weimar

Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview

2013-11-14

Hyo-Joong Kim , Jong‐Heun Lee

Thermal desorption of gases

1962-07-01

P. A. Redhead

Graphene-based gas sensors

2013-01-01

Wenjing Yuan , Gaoquan Shi

Graphene materials have been widely explored for the fabrication of gas sensors because of their atom-thick two-dimensional conjugated structures, high conductivity and large specific surface areas. This feature article summarizes … Graphene materials have been widely explored for the fabrication of gas sensors because of their atom-thick two-dimensional conjugated structures, high conductivity and large specific surface areas. This feature article summarizes the recent advancements on the synthesis of graphene materials for this purpose and the techniques applied for fabricating gas sensors. The effects of the compositions, structural defects and morphologies of graphene-based sensing layers and the configurations of sensing devices on the performances of gas sensors will also be discussed.

USE OF GLASS ELECTRODES TO MEASURE ACIDITIES IN DEUTERIUM OXIDE1,2

1960-01-01

Paul K. Glasoe , F. A. Long

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUSE OF GLASS ELECTRODES TO MEASURE ACIDITIES IN DEUTERIUM OXIDE1,2Paul K. Glasoe and F. A. LongCite this: J. Phys. Chem. 1960, 64, 1, 188–190Publication Date (Print):January 1, … ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUSE OF GLASS ELECTRODES TO MEASURE ACIDITIES IN DEUTERIUM OXIDE1,2Paul K. Glasoe and F. A. LongCite this: J. Phys. Chem. 1960, 64, 1, 188–190Publication Date (Print):January 1, 1960Publication History Published online1 May 2002Published inissue 1 January 1960https://pubs.acs.org/doi/10.1021/j100830a521https://doi.org/10.1021/j100830a521research-articleACS PublicationsRequest reuse permissionsArticle Views2895Altmetric-Citations1817LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Hydrogen Sensors and Switches from Electrodeposited Palladium Mesowire Arrays

2001-09-21

Frèdéric Favier , Erich C. Walter , Michael Zäch +2 more

Hydrogen sensors and hydrogen-activated switches were fabricated from arrays of mesoscopic palladium wires. These palladium "mesowire" arrays were prepared by electrodeposition onto graphite surfaces and were transferred onto a cyanoacrylate … Hydrogen sensors and hydrogen-activated switches were fabricated from arrays of mesoscopic palladium wires. These palladium "mesowire" arrays were prepared by electrodeposition onto graphite surfaces and were transferred onto a cyanoacrylate film. Exposure to hydrogen gas caused a rapid (less than 75 milliseconds) reversible decrease in the resistance of the array that correlated with the hydrogen concentration over a range from 2 to 10%. The sensor response appears to involve the closing of nanoscopic gaps or "break junctions" in wires caused by the dilation of palladium grains undergoing hydrogen absorption. Wire arrays in which all wires possessed nanoscopic gaps reverted to open circuits in the absence of hydrogen gas.

Luminescent probes and sensors for temperature

2013-01-01

Xudong Wang , Otto S. Wolfbeis , Robert J. Meier

Temperature (T) is probably the most fundamental parameter in all kinds of science. Respective sensors are widely used in daily life. Besides conventional thermometers, optical sensors are considered to be … Temperature (T) is probably the most fundamental parameter in all kinds of science. Respective sensors are widely used in daily life. Besides conventional thermometers, optical sensors are considered to be attractive alternatives for sensing and on-line monitoring of T. This Review article focuses on all kinds of luminescent probes and sensors for measurement of T, and summarizes the recent progress in their design and application formats. The introduction covers the importance of optical probes for T, the origin of their T-dependent spectra, and the various detection modes. This is followed by a survey on (a) molecular probes, (b) nanomaterials, and (c) bulk materials for sensing T. This section will be completed by a discussion of (d) polymeric matrices for immobilizing T-sensitive probes and (e) an overview of the various application formats of T-sensors. The review ends with a discussion on the prospects, challenges, and new directions in the design of optical T-sensitive probes and sensors.

Functionalized Carbon Nanotubes for Molecular Hydrogen Sensors

2001-09-01

Jing Kong , Michael G. Chapline , Hongjie Dai

Excellent sensors for molecular hydrogen,to be used, e.g., for leakage control in H2-based energy sources, are fabricated by functionalization of single-walled carbon nanotubes (SWNTs) with a non-continuous coating of palladium. … Excellent sensors for molecular hydrogen,to be used, e.g., for leakage control in H2-based energy sources, are fabricated by functionalization of single-walled carbon nanotubes (SWNTs) with a non-continuous coating of palladium. These sensors, with large electrical conductivity modulation in the presence of small H2 concentrations in air, show fast response and high sensitivity even at room temperature. The Figure presents an AFM image of a Pd-coated SWNT.

A Solution-Phase, Precursor Route to Polycrystalline SnO2 Nanowires That Can Be Used for Gas Sensing under Ambient Conditions

2003-12-01

Yuliang Wang , Xuchuan Jiang , Younan Xia

This paper describes a solution-based, precursor method for the facile synthesis of uniform nanowires containing rutile SnO2 nanocrystallites. In a typical procedure, nanowires of ∼50 nm in diameters and up … This paper describes a solution-based, precursor method for the facile synthesis of uniform nanowires containing rutile SnO2 nanocrystallites. In a typical procedure, nanowires of ∼50 nm in diameters and up to 30 μm in length were obtained as a white precipitate by refluxing SnC2O4·2H2O and poly(vinylpyrrolidone) in ethylene glycol. Structural analyses by XRD, FT-IR, and TGA indicate that these highly anisotropic nanostructures were formed in an isotropic medium through the aggregation of chainlike precursors that were, in turn, formed via polyol-mediated oligomerization. These nanowires could be further converted to polycrystalline SnO2 by calcination in air at 500 °C. The resultant nanowires of SnO2 were highly porous and could be used for gas sensing with improved sensitivity and reversibility under ambient conditions. We have also demonstrated that this new approach could be extended to generate polycrystalline nanowires of other metal oxides such as In2O3 and anatase TiO2.

Gas sensors using hierarchical and hollow oxide nanostructures: Overview

2009-05-05

Jong‐Heun Lee

Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

2012-02-27

Yufeng Sun , Shaobo Liu , Fanli Meng +4 more

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, … Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called “small size effect”, yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

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Simple construction of an infrared optically transparent thin-layer electrochemical cell

1991-11-01

Michael Krejčík , M. Daněk , F. Hartl

Metal oxides for solid-state gas sensors: What determines our choice?

2007-04-01

Ghenadii Korotcenkov

Nanostructured Tungsten Oxide – Properties, Synthesis, and Applications

2011-05-24

Haidong Zheng , Jian Zhen Ou , Michael S. Strano +3 more

Abstract Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their … Abstract Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their full potential. Tungsten oxides (WO x ) are unique materials that have been rigorously studied for their chromism, photocatalysis, and sensing capabilities. However, they exhibit further important properties and functionalities that have received relatively little attention in the past. This Feature Article presents a general review of nanostructured WO x , their properties, methods of synthesis, and a description of how they can be used in unique ways for different applications.

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Nanostructured Materials for Room‐Temperature Gas Sensors

2015-12-10

Jun Zhang , Xianghong Liu , G. Neri +1 more

Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed … Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high-performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high-temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room-temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room-temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure-property correlations. Finally, some future research perspectives and new challenges that the field of room-temperature sensors will have to address are also discussed.

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

2016-01-01

Minghui Sun , Shaozhuan Huang , Lihua Chen +4 more

Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to … Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.

Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructures-based gas sensors: A review

2016-06-24

Ali Mirzaei , Salvatore Gianluca Leonardi , G. Neri

Room-temperature gas sensing of ZnO-based gas sensor: A review

2017-10-12

Ling Zhu , Wen Zeng

Semiconductor metal oxide gas sensors: A review

2018-01-05

Ananya Dey

How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra

2018-12-06

Patrycja Makuła , Michał Pacia , Wojciech Macyk

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTHow To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis SpectraPatrycja MakułaPatrycja MakułaFaculty of Chemistry, Jagiellonian University in Kraków, ul. Gronostajowa 2, … ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTHow To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis SpectraPatrycja MakułaPatrycja MakułaFaculty of Chemistry, Jagiellonian University in Kraków, ul. Gronostajowa 2, 30-387 Kraków, PolandMore by Patrycja Makuła, Michał PaciaMichał PaciaFaculty of Chemistry, Jagiellonian University in Kraków, ul. Gronostajowa 2, 30-387 Kraków, PolandMore by Michał Pacia, and Wojciech Macyk*Wojciech MacykFaculty of Chemistry, Jagiellonian University in Kraków, ul. Gronostajowa 2, 30-387 Kraków, Poland*W. Macyk. E-mail: [email protected]More by Wojciech Macykhttp://orcid.org/0000-0002-1317-6115Cite this: J. Phys. Chem. Lett. 2018, 9, 23, 6814–6817Publication Date (Web):December 6, 2018Publication History Published online6 December 2018Published inissue 6 December 2018https://pubs.acs.org/doi/10.1021/acs.jpclett.8b02892https://doi.org/10.1021/acs.jpclett.8b02892editorialACS PublicationsCopyright © 2018 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views234144Altmetric-Citations2208LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (775 KB) Get e-AlertscloseSupporting Info (2)»Supporting Information Supporting Information SUBJECTS:Absorption,Electrical conductivity,Energy,Oxides,Semiconductors Get e-Alerts

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Chemical Sensing and Catalysis by One‐Dimensional Metal‐Oxide Nanostructures

2004-09-24

Andrei Kolmakov , Martin Moskovits

A Survey on Gas Sensing Technology

2012-07-16

Xiao Liu , Sitian Cheng , Hong Liu +3 more

Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different … Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches.

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Metal and Metal Oxide Nanoparticles in Chemiresistors: Does the Nanoscale Matter?

2006-01-30

Marion E. Franke , Tobias Koplin , Ulrich Simon

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Electrochemiluminescence of titanium dioxide nanomaterials for sensing applications

2025-06-25

Abdul Basıt , Muhammad Syauqi , Afiten Rahmin Sanjaya +3 more | Analytical Sciences

Photoconversion of Carbon Dioxide to Methanol Using Doped-Carbon Quantum Dots/TiO2

2025-06-25

Muhammad Wahyu Nugraha , Khee Chung Hui , Noorfidza Yub Harun +4 more | Materials science forum

Continuous emissions of carbon dioxide (CO 2 ) into the atmosphere brought several environmental problems. Photoconversion of CO 2 not only can produce value-added products (i.e. methanol) but also aim … Continuous emissions of carbon dioxide (CO 2 ) into the atmosphere brought several environmental problems. Photoconversion of CO 2 not only can produce value-added products (i.e. methanol) but also aim to reduce the environmental problems caused by CO 2 . The present work demonstrates the preparation of N-Bi co-doped carbon quantum dots/titanium dioxide (N-Bi co-doped CQDs/TiO 2 ) as a visible-light driven photocatalyst for the photoconversion of CO 2 to methanol. Hydrothermal-synthesized N-Bi co-doped CQDs were incorporated into TiO 2 nanoparticles through facile mixing method. The loading of CQDs in TiO 2 matrix resulted in a decrease of band gap to 2.75 and 2.65 eV for N-CQDs and N-Bi CQDs, respectively. Gas chromatography equipped with flame-ionization detection (GC-FID) analysis showed a methanol yield of 17 µmol/gcat from the photoconversion experiment using N-Bi-CQDs/TiO 2 photocatalyst composite. The performance of composite was assigned to the loading of N-Bi co-doped CQDs, which reduced the electron-hole recombination in TiO 2 . Doping of N-Bi played an important role in localizing the photogenerated electron-holes, essentially enhancing the electron transfer at the CQDs/TiO 2 interface. Thus, our work could provide insight into the application of CQDs-based photocatalysts in the visible-light driven photocatalytic conversion of CO 2 to value-added products.

Annealing temperature effects on SnO2 thin films: Structural, optical, morphological, and electrical properties for optoelectronics

2025-06-25

Manmohan Mishra , Sandeep Kumar Singh , Mahendra Rai | MRS Advances

Theoretical study on the adsorption of volatile organic compounds on MoSe2 surface

2025-06-25

Nguyen Ngoc Tri , The Ha Cao | Ministry of Science and Technology Vietnam

Room-temperature fabrication and characterisation of ammonia gas sensors based on FeCl3-doped polypyrrole thin films

2025-06-25

Thi Hien Hoang , Chu Van Tuan , Thanh Binh Tran +2 more | Ministry of Science and Technology Vietnam

Research on the dielectric model of asphalt mastic incorporating meso-microstructural characteristics and temperature-ultraviolet light coupling effects

2025-06-25

Bei Zhang , Yongding Niu , Yanhui Zhong +6 more | Construction and Building Materials

Visible light-assisted room-temperature hydrogen sensors using Pd/CeO2/ZnO nanocomposites

2025-06-24

Yan Wang , Mingqiao Yu , Yize Fan +5 more | International Journal of Hydrogen Energy

Optical Fiber Sensor with a Hydrophobic Filter Layer for Monitoring Hydrogen under Humid Conditions

2025-06-24

Dae-Jin Kim , Alexander Shumski , Krista K. Bullard +1 more | ACS Sensors

Real-time and remote monitoring of hydrogen concentration in underground hydrogen storage reservoirs is crucial to maintaining the integrity and safety of the storage facilities. High humidity in the underground deposits … Real-time and remote monitoring of hydrogen concentration in underground hydrogen storage reservoirs is crucial to maintaining the integrity and safety of the storage facilities. High humidity in the underground deposits interferes with hydrogen sensors, introducing inaccuracy into the hydrogen sensing measurements. A hydrophobic filter layer over a hydrogen sensing layer on an optical fiber hydrogen sensor was devised to minimize the impact of the humidity on the sensor. The hydrogen sensor coated with a hydrophobic filter layer demonstrated a significant improvement in reliable hydrogen sensing under high humidity conditions (99% RH) without severe baseline drift and reduction of transmission intensity. The optical fiber hydrogen sensor revamped with the filter layer would enable the reliable measurement of hydrogen concentration under the humid conditions expected in subsurface hydrogen storage facilities.

H2S Properties, temperature, and humidity effects on MnO2 doped MoO3 gas sensor response: Transition state theory study

2025-06-24

Mudar Ahmed Abdulsattar | Ionics

Ultra-sensitive and rapid response H2S microsensor based on Co–ZnO with ppm level detection

2025-06-24

Chen Cui , Zhiguo Zhang , Yang Zhao +1 more | Zeitschrift für Naturforschung B

Abstract In this research, a novel microsensor specifically engineered for detecting hydrogen sulfide (H 2 S) gas is introduced. Through chemical precipitation, Co x Zn 1− x O ( x … Abstract In this research, a novel microsensor specifically engineered for detecting hydrogen sulfide (H 2 S) gas is introduced. Through chemical precipitation, Co x Zn 1− x O ( x = 0, 0.05, 0.1, 0.15, 0.2) materials with a flaky structure were produced, and the resulting composite film’s structural, compositional, and morphological properties were examined using XRD, XPS, and SEM analyses. The Co x Zn 1− x O material was confirmed through XRD and XPS analyses. SEM images demonstrated that the material exhibits a porous structure and forms a uniform layer across the microsensor device. Co 0.1 Zn 0.9 O demonstrated the best gas-sensing performance. When applied on the micro-hotplate, it shows strong sensitivity and selectivity. The results of the experiments revealed that the sensor’s sensitivity is 0.02565 mA ppm −1 (95 % confidence intervals, CI: 0.0255 to 0.0258), demonstrating strong linear correlation 0.99506 (95 % CI: 0.9986 to 0.9977), and offering quick response and recovery intervals between 7.9 s (95 % CI: 7.757 to 8.043) and 6.5 s (95 % CI: 6.357 to 6.643). This gas sensor offers broad application prospects in environmental H 2 S monitoring.

Development of Nickel Graphene Oxide Composite Urea Sensor from Cathode Powder of Spent Ni-MH Batteries

2025-06-24

R. Manu , P.M. Aiswarya | Journal of The Electrochemical Society

Abstract The significant growth of energy storage technologies, primarily batteries, has revolutionized many industries. However, their disposal poses serious environmental threats and the scarcity of crucial raw materials necessitates for … Abstract The significant growth of energy storage technologies, primarily batteries, has revolutionized many industries. However, their disposal poses serious environmental threats and the scarcity of crucial raw materials necessitates for innovative recycling processes. This study explores the potential of nickel, recovered from spent Ni-MH batteries, as a key component for the development of an electrocatalytic urea sensor. Utilizing a straightforward, rapid, scalable, and environmentally benign electrophoretic deposition process, a high-performance electrode comprised of nickel and graphene oxide was formed on a copper substrate. Structural and morphological properties of the fabricated electrode were characterized by various studies such as Fourier-transform infrared-attenuated total reflectance, scanning electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray analysis. The sensing behaviour of the nickel graphene oxide composite electrode towards urea oxidation was evaluated using cyclic voltammetry, linear sweep voltammetry, chronoamperometric techniques and electrochemical impedance spectroscopy modes. The composite electrode demonstrated exceptional sensitivity and selectivity for urea detection, achieving low detection limit of &#xD;0.24 μM. The reliability of the sensor over extended periods, its consistent performance, and its suitability for practical applications were also tested. This sustainable approach addresses the growing environmental concern of battery waste and offers a promising solution for efficient urea detection.

Pt-Bimetal decorated MoS2 monolayer as sensing material for detecting dissolved gases in transformer oil: A DFT study

2025-06-24

Ying Duan , Yang Xu , Yuyang Wang | Physica Scripta

Abstract This investigation utilizes density functional theory to explore the potential of Pt-Bimetal decorated MoS2 monolayer for detecting dissolved gases, specifically CO, C2H2, and C2H4. The research reveals that the … Abstract This investigation utilizes density functional theory to explore the potential of Pt-Bimetal decorated MoS2 monolayer for detecting dissolved gases, specifically CO, C2H2, and C2H4. The research reveals that the bond is formed between Pt and defect MoS2, exhibiting a high binding energy of -11.716 eV, it exhibits excellent thermodynamic stability, dynamic stability performance and excellent moisture resistance. Between the Pt2-MoS2 and the CO, C2H2, and C2H4 are classified as chemisorption, with measured adsorption energies of -1.575 eV, -1.411 eV, and -1.628 eV, respectively. Upon exposure to CO, C2H2, and C2H4, the Pt2-MoS2 monolayer exhibits significant sensing responses of -60.2%, 68.4%, and over 100%, respectively, indicating its promise as a resistance-based sensor. Compared to other materials, Pt2-MoS2 has better adsorption performance and potential as a recyclable soluble gas.

Low-porosity Composite Film of Anodic AlOOH and Thermally Sprayed Y2O3 Film for Sensor Application

2025-06-24

C. Liu , Hsuan-Jung Chen , Shao-Fu Chang +1 more | Sensors and Materials

Monoclinic-Hexagonal Heterophase Junctions of WO3 Nanostructures with Brønsted Acid Sites for Sensitive and Selective Detection of NH3 Gas

2025-06-24

Peilin Li , Xu Chen , Bin Wang +3 more | ACS Applied Nano Materials

Manufacture of a stable MEMS gas sensor using radio-frequency sputtering deposition and the hyperthermal annealing of GaOx/CuInGaSe2 films

2025-06-24

Ming‐Fong Tsai , Shu‐Hao Fan , Ting‐Jen Hsueh | Sensors and Actuators B Chemical

An Non-metallic Nitrite Electrochemical Sensor Based on In-situ Growth of Carbon Dots on Carbon Cloth

2025-06-23

E Li , Jiao Fu , Shuang Zhou +5 more | Journal of Electrochemical Science and Technology

Enhanced Triethylamine-Sensing Characteristics of SnS2/LaFeO3 Composite

2025-06-23

Hong Wu , Xiaobing Wang , Yuxiang Chen +1 more | Chemosensors

Triethylamine (TEA), a volatile organic compound (VOC), has important applications in industrial production. However, TEA has an irritating odor and potential toxicity, making it necessary to develop sensitive TEA gas … Triethylamine (TEA), a volatile organic compound (VOC), has important applications in industrial production. However, TEA has an irritating odor and potential toxicity, making it necessary to develop sensitive TEA gas sensors with high efficiency. This study focused on preparing LaFeO3 nanoparticles modified by SnS2 nanosheets (SnS2/LaFeO3 composite) using a hydrothermal method together with sol–gel technique. According to the comparison results of the gas-sensing performance between pure LaFeO3 and SnS2/LaFeO3 composite with varying composition ratios, 5% SnS2/LaFeO3 sensor had a sensitivity for TEA that was 3.2 times higher than pure LaFeO3 sensor. The optimized sensor operates at 140 °C and demonstrates strong stability, selectivity, and long-term durability. Detailed analyses revealed that the SnS2 nanosheets enhanced oxygen vacancy (OV) content and carrier mobility through heterojunction formation with LaFeO3. This study provides insights into improving gas-sensing performance via p-n heterostructure design and proposes a novel LaFeO3-based material for TEA detection.

Low-temperature Solid-solid Interface Crystallization to Brick-mortar Structured Multicomponent Mesoporous Metal Oxides for Selective Photocatalytic Oxidation of Aromatic Alcohol

2025-06-23

Jiaqi Yang , Yuenan Zheng , Wang Ye +4 more | CCS Chemistry

Solar-Powered CO2 Capture and Release Using Amine-Functionalized Plasmonic Titanium Nitride Nanoparticles

2025-06-23

Bruno Henrique Arpini , Dreenan Shea , Mita Dasog +1 more | JACS Au

Construction of Hierarchical Porous Composite Aerogel for High‐Efficient Removal of Low‐Level Gaseous Formaldehyde

2025-06-23

Kang Xu , Xiaoxia Zhou , Heng Zhang +1 more | Small

Abstract Formaldehyde (HCHO), a pervasive indoor pollutant with chronic toxicity, poses severe health risks even at sub‐ppm levels, making its effective removal challenging. Herein, a dual‐functional aerogel integrating selective adsorption … Abstract Formaldehyde (HCHO), a pervasive indoor pollutant with chronic toxicity, poses severe health risks even at sub‐ppm levels, making its effective removal challenging. Herein, a dual‐functional aerogel integrating selective adsorption and catalytic oxidation is developed for ambient HCHO elimination. Specifically, Pt‐loaded hollow mesoporous MnO 2 (Pt@hmMnO 2 ) nanospheres are first synthesized, achieving 97.8% HCHO removal (1 mg m −3 ) under light through synergistic adsorption‐photothermal catalysis. A hierarchical porous aerogel architecture is constructed via a two‐step freezing method, embedding the Pt@hmMnO₂/cellulose nanofibers (CNF) mixture within the unidirectionally frozen chitosan (CS) matrix. The obtained 3D framework (named as CS/Pt‐CNF) features abundant ─NH 2 groups and through‐hole channels enabling selective HCHO capture and accumulation. The unique bilayer design achieves rapid HCHO reduction from 1 to 0.044 mg m −3 within 60 min, which is below the international standard (0.08 mg m −3 ). The pre‐concentration effect synergizes with the catalytic nanospheres to degrade adsorbed HCHO into CO₂ and H₂O, maintaining 97.4% efficiency after five cycles without adsorbent saturation. Mechanistic studies reveal that the macroporous CS layer facilitates gas diffusion while mesoporous Pt@hmMnO 2 ensures molecular activation, collectively enabling faster reaction kinetics than conventional powder catalysts. Such an eco‐friendly CS/Pt‐CNF aerogel demonstrates the practical potential for enclosed environments through simultaneous pollutant confinement and destruction.

Performance Analysis of Surface Acoustic Wave Hydrogen Sensor Functionalized with Pd, ZnO, and Pd/ZnO Films

2025-06-23

Anbalagan Suganya , Lakshminarayanan Sujatha , K.G. Girija | Journal of Electronic Materials

Contactless and passive humidity measurement by using ultra-thin GO nanosheet coated SAW sensor

2025-06-23

Baile Cui , Xu Gao , Zheng Zhao +6 more | Sensors and Actuators A Physical

Modeling of Chemiresistive Gas Sensors: From Microscopic Reception and Transduction Processes to Macroscopic Sensing Behaviors

2025-06-22

Zhiqiao Gao , Menglei Mao , Jinling Ma +5 more | Chemosensors

Chemiresistive gas sensors have gained significant attention and have been widely applied in various fields. However, the gap between experimental observations and fundamental sensing mechanisms hinders systematic optimization. Despite the … Chemiresistive gas sensors have gained significant attention and have been widely applied in various fields. However, the gap between experimental observations and fundamental sensing mechanisms hinders systematic optimization. Despite the critical role of modeling in explaining atomic-scale interactions and offering predictive insights beyond experiments, existing reviews on chemiresistive gas sensors remain predominantly experimental-centric, with a limited systematic exploration of the modeling approaches. Herein, we present a comprehensive overview of the modeling approaches for chemiresistive gas sensors, focusing on two critical processes: the reception and transduction stages. For the reception process, density functional theory (DFT), molecular dynamics (MD), ab initio molecular dynamics (AIMD), and Monte Carlo (MC) methods were analyzed. DFT quantifies atomic-scale charge transfer, and orbital hybridization, MD/AIMD captures dynamic adsorption kinetics, and MC simulates equilibrium/non-equilibrium behaviors based on statistical mechanics principles. For the transduction process, band-bending-based theoretical models and power-law models elucidate the resistance modulation mechanisms, although their generalizability remains limited. Notably, the finite element method (FEM) has emerged as a powerful tool for full-process modeling by integrating gas diffusion, adsorption, and electronic responses into a unified framework. Future directions highlight the use of multiscale models to bridge microscopic interactions with macroscopic behaviors and the integration of machine learning, accelerating the iterative design of next-generation sensors with superior performance.

Emerging NH3 MEMS‐Sensing Techniques and Application

2025-06-22

Y. Y. Zhang , Minmin Zhao , Chao Tan +7 more | Advanced Materials Technologies

Abstract Ammonia, a highly toxic and corrosive gas associated with human health, has important application needs in industry, food, agriculture, and other fields. In the past years, the metal‐oxide semiconductor … Abstract Ammonia, a highly toxic and corrosive gas associated with human health, has important application needs in industry, food, agriculture, and other fields. In the past years, the metal‐oxide semiconductor (MOS)‐based ammonia sensors have gained much attention and few oxides, nitrides, carbides, and their composites have been employed as the sensing materials, however, these sensors have large volume or requirement of high temperature characteristics, which hinder their application in current electronic system, especially in integrated circuits. Developing Micro‐Electro‐Mechanical System (MEMS)‐based ammonia sensors with high integration and low consumption at room temperature become more and more urgent, but is still a challenge. How to compensate the benefit contributing from the high‐ratio‐of‐surface of MOS‐sensor in MEMS‐sensor. This review briefly introduces and discusses the on‐chip ammonic sensing mechanism and the influence factors. Then, most representative chemical resistance sensors in ammonia sensing, as well as diodes and field‐effect transistors sensors related to integrated circuits are summarized. The main coupling strategies used to enhance gas sensitivity in recent years are discussed. Finally, the development prospect of high‐performance MEMS‐based ammonia sensor is discussed.

Detection Range Enhanced Highly Sensitive Niobate Nanosheet Pressure Sensors by Optimization of Substrate and Electrode Materials

2025-06-22

Zhiwen Xing , G.-P. Tang , Wenjuan Wang +6 more | Advanced Engineering Materials

With the widespread application of flexible pressure sensors in various fields, the demand for developing high‐performance flexible pressure sensors is increasing. Two‐dimensional oxide pressure sensors (2DOPSs) hold immense potential due … With the widespread application of flexible pressure sensors in various fields, the demand for developing high‐performance flexible pressure sensors is increasing. Two‐dimensional oxide pressure sensors (2DOPSs) hold immense potential due to their ultra‐high sensitivity. However, further improving the overall performance of the device remains a challenge for 2DOPSs, especially to widen the pressure sensing range of the sensor. In this article, the effect of substrate and electrode materials on the performance of the Ca 2 Nb 3 O 10 nanosheet pressure sensors is investigated. It is found that the lower the Rockwell hardness of the electrodes of the device, the easier the substrate material deforms under pressure, and the lower the device pressure threshold, the higher the sensitivity. The optimization of the substrates and electrodes yields Ca 2 Nb 3 O 10 nanosheet pressure sensors with sensitivity up to 10 5 kPa −1 in a large detection range, fast response time (83/165 ms) and good stability. This work provides guideline for further development of 2DOPSs.

Native Oxide MoO₂– MoSe₂ Heterostructure‐Based Self‐Powered Gas Sensor for Selective NO₂ and H₂ Detection

2025-06-22

D.P. Mondal , D. K. Sharma , R Karthik +4 more | Small

Abstract A single‐step chemical vapor deposition method is reported to synthesize native oxide metal ‐semiconductor MoO₂–MoSe₂ heterostructure flakes for self‐powered gas sensing. Two types of flakes, S1 and S2, with … Abstract A single‐step chemical vapor deposition method is reported to synthesize native oxide metal ‐semiconductor MoO₂–MoSe₂ heterostructure flakes for self‐powered gas sensing. Two types of flakes, S1 and S2, with distinct compositions, are analyzed using Raman, photoluminescence spectroscopy, Atomic Force Microscopy, X‐ray and UV Photoelectron Spectroscopy, and High‐Resolution Transmission Electron Microscopy (HRTEM). TEM and Energy Dispersive Spectroscopy (EDS) mapping confirm a clear interface and compositional gradation in the heterostructures. Sample S1, predominantly MoO₂ and highly metallic, exhibits minimal photoresponse but shows selective H₂ detection at room temperature. In contrast, S2, with a top‐down MoO₂–MoSe₂ structure, demonstrates broadband optical photoresponse and high sensitivity toward NO₂ with a detection limit of 10 ppm. The enhanced performance at low (few mili volts) or zero bias is attributed to photocarriers generated at the heterojunction and NO 2 /MoSe 2 /MoO 2 interface‐driven interactions under visible light exposure. The response is further found to be enhanced significantly in the presence of humidity, making it suitable for detection in humid environments. This interface engineering strategy enables the development of room‐temperature, self‐powered gas sensors with high selectivity and sensitivity, paving the way for future nanoelectronic and MEMS‐integrable sensing devices.

Automation of the drop-casting deposition method for polymeric sensing films over a quartz crystal microbalance

2025-06-21

Alexis Iván Bravo-Sánchez , J. Castillo-Mixcóatl , Miguel Ángel Moreno-Acosta +6 more | Deleted Journal

Recent Advances in Resistive Gas Sensors: Fundamentals, Material and Device Design, and Intelligent Applications

2025-06-21

Peiqingfeng Wang , Shusheng Xu , Xuerong Shi +3 more | Chemosensors

Resistive gas sensors have attracted significant attention due to their simple architecture, low cost, and ease of integration, with widespread applications in environmental monitoring, industrial safety, and healthcare diagnostics. This … Resistive gas sensors have attracted significant attention due to their simple architecture, low cost, and ease of integration, with widespread applications in environmental monitoring, industrial safety, and healthcare diagnostics. This review provides a comprehensive overview of recent advances in resistive gas sensors, focusing on their fundamental working mechanisms, sensing material design, device architecture optimization, and intelligent system integration. These sensors primarily operate based on changes in electrical resistance induced by interactions between gas molecules and sensing materials, including physical adsorption, charge transfer, and surface redox reactions. In terms of materials, metal oxide semiconductors, conductive polymers, carbon-based nanomaterials, and their composites have demonstrated enhanced sensitivity and selectivity through strategies such as doping, surface functionalization, and heterojunction engineering, while also enabling reduced operating temperatures. Device-level innovations—such as microheater integration, self-heated nanowires, and multi-sensor arrays—have further improved response speed and energy efficiency. Moreover, the incorporation of artificial intelligence (AI) and Internet of Things (IoT) technologies has significantly advanced signal processing, pattern recognition, and long-term operational stability. Machine learning (ML) algorithms have enabled intelligent design of novel sensing materials, optimized multi-gas identification, and enhanced data reliability in complex environments. These synergistic developments are driving resistive gas sensors toward low-power, highly integrated, and multifunctional platforms, particularly in emerging applications such as wearable electronics, breath diagnostics, and smart city infrastructure. This review concludes with a perspective on future research directions, emphasizing the importance of improving material stability, interference resistance, standardized fabrication, and intelligent system integration for large-scale practical deployment.

Giant Chemo-Resistive Response of POSS Nano-Spacers in PS- and PMMA-Based Quantum Resistive Vapour Sensors (vQRS) Used for Cancer Biomarker Analysis

2025-06-21

Abhishek Sachan , Mickaël Castro , Veena Choudhary +1 more | Chemosensors

The detection of volatile organic compound (VOC) biomarkers from the volatolome for the anticipated diagnosis of severe diseases such as cancers is made difficult due to the presence of high … The detection of volatile organic compound (VOC) biomarkers from the volatolome for the anticipated diagnosis of severe diseases such as cancers is made difficult due to the presence of high quantities of H2O in the collected samples. It has been shown that water molecules tend to compete or combine themselves with analytes, which requires either their removal or the development of more sensitive and discriminant sensors. In this later prospect, a positive effect of poly(hedral oligomeric silsesquioxanes) (POSS) is sought out to enhance the sensitivity of carbon nanotube-based quantum resistive vapour sensors (vQRS). POSS, once copolymerized with methyl methacrylate or styrene, can be used as nano-spacers amplifying the disconnection of the nano-junctions due to swelling of the polymer upon the diffusion of VOC. The amplitude of this phenomenon, which is at the origin of the chemo-resistive behaviour of vQRS, was compared with that of homologue transducers made of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA)-coated carbon nanotube (CNT) random networks. The presence of POSS in PS-based sensors has enhanced their sensitivity by 213 times for toluene, by 268 times for acetone, by 4 times for ethanol, and by 187 times for cyclohexane. Similarly, the presence of POSS in PMMA chains increases the sensitivity of sensors to cyclohexane by 10 times, to ethanol by 45 times, to toluene by 244 times, and to acetone and butanone by 4 times. All transducers were made by spray layer by layer (sLbL) to obtain a hierarchically structured conducting architecture. The transducers’ surface was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) to observe the CNT coating and dispersion level in the matrix. All sensors were tested with twenty-one VOC part of lung and skin cancer biomarkers by using a dynamic vapour analysis (DVA). The vQRS based on POSS copolymers demonstrated much larger chemo-resistive responses (AR) than the sensors based only on pure polymers and were found to be very selective towards cyclohexane and hexene-1. The PMMA-co-POSS/CNT sensor was able to detect down to 12 ppm of VOC with a very high signal-to-noise ratio (SNR) and to discriminate six VOC among them all with a PCA (principal component analysis) projection.

Atomic cubic gauche nitrogen polymerized at ambient pressure

2025-06-20

Runteng Chen , Jun Zhang , Zelong Wang +5 more | Science China Physics Mechanics and Astronomy

Dynamic Growth Configuration of 2D‐SnS2 Nanoflakes for Humidity‐Resistant NO2 Monitoring System: Mechanistic Insights and Environmental Applications

2025-06-20

R. Abimaheshwari , R. Abinaya , C. Suresh Prasanna +2 more | Small

Abstract SnS 2 was fabricated using atmospheric pressure chemical vapor deposition for efficient nitrogen dioxide ( NO 2 ) detection at room temperature. The deposition of SnS 2 on the … Abstract SnS 2 was fabricated using atmospheric pressure chemical vapor deposition for efficient nitrogen dioxide ( NO 2 ) detection at room temperature. The deposition of SnS 2 on the silicon dioxide/silicon (SiO 2 /Si) substrate was tuned by varying the distance between the tin source and the substrate (D ss ). The sensing performance of all the fabricated sensors has been scrutinized towards NO 2 gas in the temperature range of 30 °C to 100 °C. Among them, the D ss −2 sensor exhibited a superior sensing performance of 302% against 40 ppm of NO 2 at 30 °C, with response and recovery time of 32 s and 162.5 s, respectively, enduring over 80 days with reliable stability. The adsorption fitting with Freundlich adsorption isotherm model and Gibbs free energy calculation validates the fabricated sensor comprises heterogenous binding sites, with exothermic behaviour and high spontaneity. Further, the D ss −2 sensor was employed to construct a prototype sensor module for the real‐time detection of NO 2 gas at ambient temperature, thereby expanding the potential practical applications for NO 2 detection. Thus, this work paves a crucial ideology for the growth regulation of 2D layered materials with potent detection of NO 2 .

Controlled Synthesis of Tungsten Oxide Nanomaterials with Different Morphologies and Their Gas-Sensing Properties for Formaldehyde in Vegetables

2025-06-20

Weihao Wu , Yaochong Yang , Cheng Zhao +5 more | Biosensors

Formaldehyde is illegally applied to vegetables by vendors as a preservative to extend their shelf life, and it poses health risks to consumers. Herein, a series of WO3 with different … Formaldehyde is illegally applied to vegetables by vendors as a preservative to extend their shelf life, and it poses health risks to consumers. Herein, a series of WO3 with different morphologies were synthesized and employed as the sensing material in gas sensors to detect formaldehyde in vegetables rapidly. Among all the samples, the WO3 nanoplate sensor exhibited the best sensitivity (16.5@200 ppm), a rapid response/recovery time (10/12 s), superior selectivity, and a low limit of detection (500 ppb). This was mainly attributed to its abundant mesopores and large specific surface area, which enhanced the formaldehyde adsorption capacity and adsorption/desorption rates while providing more active sites, thereby improving the sensor’s response speed and resistance variation range. The WO3 nanoplate sensor also achieved reliable formaldehyde detection in actual vegetable samples (baby cabbage). This study provides systematic guidance for optimizing the gas-sensing performance of functional materials. It establishes a foundation for developing rapid, non-destructive formaldehyde detection technologies applicable for vegetable quality control.

A Highly Sensitive Formaldehyde Gas Sensor Based on Ag2O and PtO2 Co-Decorated LaFeO3 Nanofibers Prepared by Electrospinning

2025-06-20

Xin Wang , Fei Song , Huaian Fu +6 more | Sensors

The widespread use of formaldehyde in both industrial and household products has raised significant health concerns, emphasizing the need for highly sensitive sensors to monitor formaldehyde concentrations in the environment … The widespread use of formaldehyde in both industrial and household products has raised significant health concerns, emphasizing the need for highly sensitive sensors to monitor formaldehyde concentrations in the environment in real time. In this study, we report the fabrication of a highly sensitive formaldehyde gas sensor based on Ag2O and PtO2 co-decorated LaFeO3 nanofibers, prepared by electrospinning, with an ultra-low detection limit of 10 ppb. Operating at an optimal temperature of 210 °C, the sensor exhibits high sensitivity, with a response value of 283 to 100 ppm formaldehyde—nearly double the response of the Ag-only decorated LaFeO3 sensor. Additionally, the sensor demonstrated good selectivity, repeatability, and long-term stability over 80 days. The enhanced sensitivity is attributed to the strong adsorption ability of Ag towards both oxygen and formaldehyde, Ag’s catalytic oxidation of formaldehyde, PtO2’s catalytic action on oxygen, and the spillover effect of PtO2 on oxygen. This sensor holds significant potential for environmental monitoring due to its ultrahigh sensitivity and ease of fabrication.

Coaxial electrospun of ZnO-SnO2 core-shell solid nanofibers for ethanol vapor sensing

2025-06-20

Xiaoling Xie , Haotian Jiang , Wei Li | Journal of Alloys and Compounds

Efficient Implementation of MINT-Based Chemiresistor Arrays for Artificial Olfaction

2025-06-20

Michele Galvani , Alejandro López‐Moreno , Natalia Martín Sabanés +5 more | Journal of the American Chemical Society

We demonstrate the possibility of using an array of MINT-based chemiresistors for the selective detection of VOCs at room temperature. Four new types of MINTs with different functional groups (MINTALKENE … We demonstrate the possibility of using an array of MINT-based chemiresistors for the selective detection of VOCs at room temperature. Four new types of MINTs with different functional groups (MINTALKENE (X:-CH = CH2), MINTCOOMe (X:-COOMe), MINTCOOH (X:-COOH), and MINTOH (X:-CH2OH)) were specifically synthesized to prepare a set of six sensing layers, which included, in addition to the new MINTs, a pristine SWNTs layer and a MINTXYLENE layer. The functionalized sensing layers were tested by exposing them to NH3, NO2, EtOH, IPA, acetone, benzene, and NaClO vapors in the ppm range. We showed that MINT functionalization enhances response to analytes with respect to pristine SWNTs. When assembled into an array, our sensing layers can operate at room temperature as an electronic nose, disclosing the possibility of using these layers in low-power-consumption wearable devices. Correlation plots, PCA, and UMAP analysis show that a remarkable discrimination of ammonia with respect to interfering gases can be reached by the e-nose. Gas mixtures were also discriminated, as shown for NH3/ethanol, acetone/ethanol, and isopropanol/acetone mixtures, which are relevant in view of breathomics applications. The efficient preparation method of sensing layers allows for an improvement of performance, as shown for one of the best performing chemiresistors in the set, resulting in a sensitivity increase (up to 10×) and a dramatic reduction of response and recovery times.

Nanoscale Metal Oxide Heterojunction Chemiresistive Gas Sensor: A Review

2025-06-20

S. Giri , Julian W. Gardner , Prasanta Kumar Guha +2 more | Nano Futures

Abstract Nano-material based resistive gas sensors are gaining in popularity because of their small size, low cost, and simple integration with analogue interface electronics. In gas sensors, semiconducting metal oxides … Abstract Nano-material based resistive gas sensors are gaining in popularity because of their small size, low cost, and simple integration with analogue interface electronics. In gas sensors, semiconducting metal oxides are most widely used as the sensing layer, because they offer high sensitivity to gases and have a low detection limit (ppb to ppm). However, metal oxides suffer from a poor selectivity, because they generally respond to both oxidising and reducing gas molecules. In addition, they can suffer from baseline drift/stability and in some cases degradation under humid conditions. Some of these drawbacks can be ameliorated using metal oxide heterojunctions. A metal oxide heterojunction is the formation of a junction between two materials with different work functions. The metal oxide heterojunction can improve sensor performance through a controlled depletion region (band bending), charge transfer, catalytic effects, and improved gas adsorption kinetics. They can also permit a lower operating temperature (hence lower power), improved sensitivity, faster response and better stability. This review paper discusses in detail the different techniques to synthesise metal oxide heterojunctions, the sensing mechanisms, and how they can be a generation of improved gas sensors. Finally, we discuss the emergence of artificial intelligence to enable the identification of gas type and concentrations from multi-component environments.

Multi-Objective Bayesian Optimization of Eco-Friendly Gas Mixtures for Resistive Plate Chambers

2025-06-20

Pit Bechtold , Dario Stocco , Christian M. Franck | Machine Learning Science and Technology

Abstract Developing environmentally friendly gas mixtures for Resistive Plate Chambers (RPCs) has been a research focus for the last few years. This study presents a novel approach for autonomous optimization … Abstract Developing environmentally friendly gas mixtures for Resistive Plate Chambers (RPCs) has been a research focus for the last few years. This study presents a novel approach for autonomous optimization of the detector performance and environmental impact of gas mixtures and enabling a more efficient evaluation for finding a suitable replacement for RPCs. The proposed framework is built upon multi-objective Bayesian optimization (BO) with Pareto front prediction and per-point noise implementation. This work fills a research gap by applying advanced optimization tools, specifically BO, to challenges in gas insulation systems and electrical engineering: An approach that is not commonly applied in the field. This framework can be applied in both experimental and simulation studies, and is applied here in a study of CO2-based standard mixtures, intending to enhance avalanche-to-streamer separation and to reducing the gas mixture's CO2 equivalent. The resulting optimization includes 259 simulated gas mixtures and indicates that reducing the environmental impact of CO2-based standard mixtures always comes at the cost of reducing the separation. No mixture with performance superior to or similar to the gas mixtures currently in use could be found while also significantly reducing the CO2e. This optimization yields a detailed simulated data set for gas mixture replacement in RPCs, showing a hypervolume improvement that exceeds traditional methods within 33% of the number of iterations, thus eliminating the need for time-consuming traditional parameter space sampling approaches. Future enhancements utilizing ultralow GWP gases, such as HFO-1234ze(E), or additional objectives, can be realized within this novel current framework.

Metal-Oxide-Semiconductor Nanostructure/NiO Microparticle Heterojunctions Formed on Metallic Foils for Sensitive Chemiresistive Ion Sensors

2025-06-20

Yoshinari Kimura , Hironori Tohmyoh | ACS Omega

Impact of dopant synergistic effects on SnO2 (110) surface and sub-surface layers for enhanced bidentate formaldehyde adsorption: a DFT study

2025-06-20

Shaheen Gulshanah , Ayon Bhattacharjee | Indian Journal of Physics

Probing the Challenge of P‐Type Semiconductors in Long‐Chain VOC Detection: 3D Micro‐Flower Zinc Cobaltate Heterojunction Sensors

2025-06-20

Kewei Liu , Zichen Zheng , Yiwen Zhou +3 more | Advanced Science

Abstract Tetradecane, a long‐chain alkane recently recognized as a volatile marker for early‐stage mildew detection in stored grains and as a reference material in hydrocarbon studies, presents significant challenges for … Abstract Tetradecane, a long‐chain alkane recently recognized as a volatile marker for early‐stage mildew detection in stored grains and as a reference material in hydrocarbon studies, presents significant challenges for detection due to its inherent low reactivity and substantial molecular size. This study reports the synthesis of a microflower‐like Fe@WO 3 / ZnCo 2 O 4 heterostructure for effective tetradecane sensing. The Fe@WO 3 / ZnCo 2 O 4 n‐p junctions demonstrated significant alterations in electrical conductivity upon exposure to tetradecane at room temperature. The sensor achieved a reasonable detection limit of 78.4 ppb and a rapid recovery time of 36 s. The remarkable sensing performance is attributed to the synergistic interactions among multiple heterojunction interfaces, doping‐induced active sites, the presence of oxygen vacancies, high‐energy crystallographic facets, reduced grain size, and enhanced crystallinity, as supported by density functional theory calculations and molecular dynamics simulations. This work identifies a promising candidate for the detection of distinct volatile organic compounds, warranting further exploration in agricultural and emission monitoring applications while addressing a critical gap in metal oxide semiconductor sensors for the detection of large‐molecule gases.

Design of an Infrared Wide-Angle Metalens for Medical Endoscopic Imaging Systems

2025-06-20

Xin-Jie Zhao , Peng Xing , Shaohui Xu +3 more | Optics Express

PrFeTiO5-Based Chemoresistive Gas Sensors for VOCs Detection

2025-06-20

Danial Ahmed , Elena Spagnoli , Adil Chakir +5 more | Chemosensors

The development of effective, cost-efficient, and printable solid-state gas sensors for the detection of volatile organic compounds is of great interest due to their wide range of applications, spanning from … The development of effective, cost-efficient, and printable solid-state gas sensors for the detection of volatile organic compounds is of great interest due to their wide range of applications, spanning from real-time indoor monitoring to emerging fields such as non-invasive medical diagnostics. However, gas sensors encounter difficulties in discovering materials that have both good selectivity and sensitivity for numerous volatile organic compounds in both dry and humid settings. To expand the class of sensing materials, the current study investigates the sensing performance of solid solutions based on a rare-earth metal oxide. Pr, Fe, and Ti oxide solid solutions were produced using a solid-state technique, with thermal treatments at varied temperatures to tune their structural and functional properties. The powders were used, for the first time, to produce chemoresistive sensors, which showed promising sensing capabilities vs. ethanol, acetone, and acetaldehyde. The sensors were characterized by varying the concentration of the target gases from 1 to 50 ppm in a controlled environment, with the relative humidity ranging from 2 to 40%. The findings bring a turning point, leading to fruitful paths for the development of Pr-based solid solutions-based chemoresistive gas sensors for the detection of volatile organic compounds.

Synergistic oxygen plasma and variable-valence metal (Ni/Mn) doping strategy engineering enhanced low-temperature H2S sensing mechanism in In2O3 nanotubes

2025-06-19

Yuchen Jiang , Jiaru Yang , Linlin Dong +6 more | Sensors and Actuators B Chemical

Development of highly sensitive Cu doped ZnFe2O4 nanoparticles-based xylene sensor

2025-06-19

G Maragathavalli , S. Mugundan , J. Rajeev Gandhi +3 more | Applied Physics A

Unveiling the room-temperature chemiresistive NH₃ adsorption capability of NiO doped PPy nanocomposite with DFT interpretations

2025-06-19

Ratindra Gautam , Shivani Chaudhary , Vivek Kumar Nautiyal +2 more | Nano Express

Abstract he responsive and selective identification of ammonia at room temperature is crucial for effective environmental pollution control and for preventing health hazards in industrial settings. The excellent electrical properties … Abstract he responsive and selective identification of ammonia at room temperature is crucial for effective environmental pollution control and for preventing health hazards in industrial settings. The excellent electrical properties of nickel (Ni) and the sensing capabilities of polypyrrole (PPy) have been synergistically combined to achieve enhanced ammonia sensitivity. NiO-doped PPy nanoparticles were synthesized via an oxidative polymerization route, and the resulting nanomaterials were thoroughly characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-visible spectroscopy. The bandgap, determined from UV-visible spectroscopy data, was found to be 4.6 eV. The sensor exhibited a maximum response of 0.29 at 225 ppm of NH3, with minimum response and recovery times of 11 seconds and 18 seconds, respectively. The limit of detection has been calculated by using the linear curve fitting of sensor response and found to be 17.31 ppm. Density Functional Theory (DFT) simulations were employed to investigate the adsorption of NH3 molecules on NiO-doped PPy nanoparticles. The simulations revealed changes in dipole moment, adsorption energy, and HOMO-LUMO gaps upon NH3 adsorption. Additionally, Density of States (DOS) plots indicated alterations in the composition of the HOMO-LUMO levels due to NH3 adsorption. This study demonstrates the potential of NiO-doped PPy nanoparticles as highly responsive and selective ammonia gas sensors, providing rapid detection and reliable performance at room temperature.

Macroporous ZnO Nanoreactors Decorated with Amorphous CoOx Clusters for Room Temperature Sensors of Acetone in Breath

2025-06-19

Xiaoyu Liu , J Li , Haiyang Wang +6 more | ACS Applied Nano Materials

Chemiresistive NO2 Gas Sensor Based on RuO2/MoS2 Composite

2025-06-19

Shubham V. Patil , Roopa Kishore Kampara , A. Venktesan +5 more | Journal of Alloys and Compounds

Multifunctional dopamine-coated FeVO4 composites applied in supercapacitors and sensors for human motion, gas and light monitoring, and secure transmission of information

2025-06-19

W.X. Zhang , Xiaohui Zhao , Guo Ye +5 more | Chemical Engineering Journal

Constructing adsorption site-enhanced ZnWO4/Li6W2O9 heterojunction sensing electrode for efficient performance in impedancemetric NO2 sensor

2025-06-19

Tianshou Zhao , Weiwei Meng , Yuehua Li +4 more | Rare Metals